Photodynamic therapy (PDT), emerging as a minimally invasive therapeutic modality with precise controllability and high spatiotemporal accuracy, has earned significant advancements in the field of cancer and other non-cancerous diseases treatment. Thereinto, type I PDT represents an irreplaceable and meritorious part in contributing to these delightful achievements since its distinctive hypoxia tolerance can perfectly compensate for the high oxygen-dependent type II PDT, particularly in hypoxic tissues. Regarding the diverse type I photosensitizers (PSs) that light up type I PDT, aggregation-induced emission (AIE)-active type I PSs are currently arousing great research interest owing to their distinguished AIE and aggregation-induced generation of reactive oxygen species (AIE-ROS) features. In this review, we offer a comprehensive overview of the cutting-edge advances of novel AIE-active type I PSs by delineating the photophysical and photochemical mechanisms of the type I pathway, summarizing the current molecular design strategies for promoting the type I process, and showcasing current bioapplications, in succession. Notably, the strategies to construct highly efficient type I AIE PSs were elucidated in detail from the two aspects of introducing high electron affinity groups, and enhancing intramolecular charge transfer (ICT) intensity. Lastly, we present a brief conclusion, and a discussion on the current limitations and proposed opportunities.

Motivated by the advantages of AIEgens in diversifying energy species and modulating energy transformation, the application of AIEgens based on the energy conversion of solar, chemical, mechanical, and electrical energies are summarized.

Fluorescence imaging in the second near-infrared window (NIR-II, 1000–1700 nm) has emerged as a powerful tool for in vivo bioimaging, offering deep-tissue penetration alongside superior spatiotemporal resolution and contrast. The development of high-performance probes is essential for achieving high-quality imaging outcomes. Owing to their unique photophysical properties, aggregation-induced emission (AIE) luminogens have been recognized as an ideal platform for constructing advanced NIR-II organic fluorescent probes. However, the brightness of current NIR-II AIE probes remains suboptimal concerning practical applications due to intrinsic molecular constraints and environmental quenching effects. To address these issues, a high-brightness NIR-II AIE nanoprobe, TT12,8-B NPs, was developed based on the proposed design strategy of increasing molecular alkyl lengths, which simultaneously enhances aggregate hydrophobicity and expands intermolecular packing distance, synergistically improving both molar absorptivity and quantum yield (QY). Notably, the optimized TT12,8-B NPs exhibit nearly fourfold higher brightness than TPE-BBT NPs, which is one of the highest-QY NIR-II AIE probes reported currently. Coupled with optimal particle size, good water dispersibility, outstanding photostability and biosafety, TT12,8-B NPs enabled high-clarity multiscale vasculature imaging in mice and rabbits, attaining an unprecedented signal-to-background ratio exceeding 10 and a record-high vascular resolution of 49 μm in diameter, setting new benchmarks in NIR-II fluorescence angiography. Furthermore, the exceptional angiographic performance of TT12,8-B NPs further facilitated early malignant tumor detection and discrimination between nascent and established tumors. This work not only introduces an excellent NIR-II fluorescent probe but also establishes an innovative molecular design paradigm to guide the development of brighter NIR-II organic emitters.